A protein (or polypeptide)-lipid complex, classified as a proteolipid was isolated from the Walker carcinosarcoma 256 (W256) and is designated as neoproteolipid-W(NPL-W). Systematic screening of different animal and some human tumors revealed that some tumors have NPL-W, whereas other tumors (e.g. rat Morris hepatoma 5123) have a neoproteolipid which has different chromatographic properties. This neoproteolipid was designated as neoproteolipid-S (NPL-S). NPL-W is composed of neutral glycosphingolipids, polypeptides (or proteins) and small quantities of other lipids, NPL-S has a similar composition, but instead of neutral glycosphingolipids it contains gangliosides. The presence of neoproteolipids (without identification of the type of neoproteolipids) was demonstrated also in blood sera of cancer patients with advanced forms of cancer and PNL-W in rats with W256, whereas sera from normal control human subjects and normal rats do not contain measurable quantities of these protein-lipid complexes. Preliminary experiments demonstrated that blood sera from Morris hepatoma 5123 bearing rats contain 6-7 times more NPL-S than sera from normal rats. The general aim of this project is to investigate the biochemistry of these neoproteolipids and possibly to use the level of these neoproteolipids in blood serum as a tool for the detection of malignancy and/or efficacy in the medical treatment of cancer. The study of the chemical composition of NPL-W and NPL-S will be continued by using gas- liquid chromatography, other kinds of chromatography, and microchemical procedures. The relationship between the alteration of glycosphingolipid patterns in tumors and the formation of neoproteolipids also will be investigated. Studies on the levels of NPL-S in blood serum of Morris hepatoma bearing rats and normal rats will be continued. Using minimal blood serum quantities from cancer bearing rats and normal rats a method for simultaneous determination of NPL-S and NPL-W (identification and quantitative determination) will be worked out. Such procedures are necessary in order to start screening for neoproteolipids in blood sera samples from normal subjects, cancer patients and patients in the "precancerous" stage.